Solid state imaging devices, which are widely used for video cameras and still cameras and the like, are provided in the form of a package, in which an imaging element such as a CCD or the like is mounted on a base made of an insulating material, with the photodetecting region being covered by a transparent plate. In order to make the device more compact, the imaging element is mounted as a bare chip on the base. Referring to FIG. 7, the following is an explanation of the solid-state imaging device disclosed in JP H5-267629A as a conventional example of these types of solid-state imaging devices.
In FIG. 7, numeral 21 denotes a base, on the top face of which is formed a recess portion. An imaging element chip 22 is formed in the center of the recess portion. The base 21 is provided with a lead terminal 24, a lead side pad 25 of which is connected by a bonding wire 26 made of metal to a bonding pad 23 of the imaging element chip 22. A package is formed for the purpose of protecting the imaging element chip 22 by integrally forming a rib 28 on an upper surface of a peripheral portion of the base 21 and fastening a transparent sealing glass plate on top of it.
This type of solid-state imaging device is mounted on a circuit board with the sealing glass plate 27 facing upward, as shown in FIG. 7, and the lead terminals 24 are used to connect it to the electrodes on the circuit board. Although not shown in the drawings, a lens barrel incorporating an imaging optical system whose relative position to the photodetecting region formed in the imaging element chip 22 is adjusted with a predetermined precision is mounted on top of the sealing glass plate 27. During the imaging operation, object light that has passed through the imaging optical system incorporated in the lens barrel is focused on the photodetecting region and photoelectrically converted.
The above-described conventional example of a solid-state imaging device has a housing structure in which the rib 28 is formed on the upper surface of the peripheral portion of the base 21. The casting mold for molding the housing with resin is matched to the housing specification and must be made for each product, leading to an increase in the manufacturing cost.
For that reason, a process using a wiring board which can be manufactured more cheaply, and using a process of molding resin ribs onto the wiring board is conceivable. However, when molding resin ribs onto the wiring board, deformations of the housing such as warping and twisting tend to occur, caused by the difference in thermal expansion between the wiring board containing metal wires and the rib made of a resin. This problem is particularly conspicuous when manufacturing a plurality of housings for solid-state imaging devices all together.
Also, for the purpose of suppressing the scatter of light incident on the internal space of the housing, the ribs sometimes are provided with a taper. The taper direction differs according to the design of the solid-state imaging device. However when the taper direction is provided such that the rib width increases away from the board surface (called a “reverse taper” below), an impediment to rib resin molding develops. That is to say, if the housing structure is formed integrally with the rib 28 on the upper surface of the peripheral portion of the base 21, or if the rib is resin-molded onto the wiring board, mold release after molding of the portion of the forming die which forms the internal space of the housing becomes problematic because of the rib's reverse taper.